In alternating chapters, the identical-twin Tatum sisters of Louisville, Kentucky--straitlaced Bert (newly divorced, mother of college-age kids, Claiborne-attired) and earthy Nan (single, a country-and-western d.j.)--narrate their near-fatal, sometimes farcical involvement with a series of ugly murders. The mayhem commences when a handsome stranger greets Bert on the street as if she were an old girlfriend--and then turns up dead a few hours later. Soon the sisters are being followed, shot at, threatened by phone, and their homes are vandalized. So, getting no help from the oafish homicide cops (who regard them as publicity hounds), the sisters sleuth on their own--interviewing the dead man's wife (the next to die), tracking a suspect to a seedy hotel, and uncovering the key plot point here: That the new killings are linked to the unsolved murders, 25 years ago, of a couple for whom the Tatum twins babysat! And there'll be kidnapping (Nan's) and a car-chase (prim Nan in the hot seat) before the far-fetched yet faintly disturbing windup. (Think Ross Macdonald in his darkest Oedipal mode.) Too grim and gimmicky for steady laughs, but, with rueful one- liners (about Bert's lecherous ex, for example) and droll commentary on twinship (the authors are identicals, too), the odd- couple sisters give an engaging lift to this uninspired, hardworking entertainment.